Display screen or portion thereof with transitional graphical user interface



1. Display screen or portion thereof with transitional graphical user interface

2. Display screen or portion thereof with transitional graphical user interface

3. Display screen or portion thereof with transitional graphical user interface

4. Display screen or portion thereof with transitional graphical user interface

4.1 : Front, the first image in a sequence

4.2 : Front, the second image in a sequence

The outer perimeters shown in broken lines illustrate a display screen or portion thereof and form no part of the claimed designs; the remaining broken lines in the figures illustrate portions of the graphical user interface that form no part of the claimed designs; the appearance of the transitional image sequentially transitions between the images shown in reproductions 4.1-4.2; the process or period in which an image transitions to another image forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 